Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/27/22

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 826 PM PDT Sun Jun 26 2022

.SYNOPSIS...26/501 PM.

Hot and dry conditions will persist through Tuesday as a strong
ridge of high pressure remains over the region. A low pressure
system will move into the area on Wednesday, bringing southwest
flow aloft and gradually cooling temperatures. Overnight low
clouds will continue to affect coastal areas through Wednesday,
and may extend to some coastal valleys as well.

&&

.SHORT TERM (SUN-WED)...26/824 PM.

Upper level ridge of high pressure will continue to build across
Southwest California through Monday, with continued hot and dry
conditions across inland areas. Triple digit heat was more
widespread today, with Woodland Hills coming in at 104 degrees,
Palmdale at 103, and Paso Robles observing 106 degrees. A shallow
marine layer depth will continue to moderate coastal areas.
Latest ACARS soundings showing marine layer depth around 700 feet
across the LA Basin, with further lowering possible by morning.
Satellite imagery showing low clouds and fog rolling back into
the Central Coast this evening, and will most likely develop
across other coastal areas overnight into Monday morning. With a
low and strong inversion in place, there is also the potential for
patchy dense fog tonight and again Monday night, which may
require dense fog advisories. The strong inversion and continued
onshore flow from the west will likely support some low clouds
and fog lingering well into the afternoon for some west facing
beaches.

The main story will continue to the hot temperatures and low
humidities across inland areas through Monday, with heat
advisories in effect for many inland areas of Southwest
California. Most inland areas will likely see an additional 1-3
degrees of warming on Monday with highs generally ranging between
95 and 105 degrees for many valley, lower mountain, and desert
locations, except up to 108 degrees in the San Luis Obispo County
Interior valleys. Coastal areas will continue to be more mild
with highs mostly in the 70s and 80s. Also of note is some gusty
sundowner winds this evening across western foothills/canyons of
the Santa Barbara south coast where gusts of 25 to 35 mph will be
common, except isolated gusts to 40 mph near Gaviota. While the
wind speeds are not particularly strong, they are bringing warm
and dry air into those areas as evident by temperatures climbing
well into the 80s during the past few hours.

While areas south of Point Conception will likely see some
cooling on Tuesday due to stronger onshore flow, a slight
offshore wind component Tuesday morning will potentially maintain
hot temperatures across interior areas of SLO county into Tuesday
afternoon, which may prompt the extension of the heat advisory for
SLO county interior valleys/mountains. The hot temperatures and
low humidities (including poor overnight recoveries) will bring an
increased risk of fire activity across inland areas through
Tuesday,

*** From previous discussion ***

There will perhaps be some slight cooling focused in LA/VTA
counties on Tuesday, but additional warming is possible west of
the mountains in SLO/SBA counties due to an offshore push from the
east. 950 mb temperatures of 25-30 C across foothill to lower
mountain slopes on Tuesday will support low temperatures in the
high 70s or low 80s, increasing heat impacts for these areas.

The greatest uncertainly each day in high temps is near the
margin of the marine layer (as is typical), which is this case is
near coastal areas where daytime highs may be off by locally 5+
degrees.

The ridge of high pressure does slide into a somewhat favorable
position for a monsoon push into southern California, though
ensemble guidance is still muted with moisture and convection
response.  The California/Nevada RFC says that on Monday and
Tuesday there may be enough moisture and instability to generate
some very scattered showers and thunderstorms over southeast CA
and the higher terrain from southwest San Bernardino county down
across San Diego county. So in the eastern San Gabriel mountains
there is a non-zero, though very small chance of convection.

Should clouds materialize by Tuesday afternoon, it could support
a few degrees of cooling for portions of LA county.

On Wednesday the upper level pattern begins to change and upper-
level flow will switch to southwesterly and the gradual height
falls will begin. The switch to southwest flow should shove any
lingering monsoon moisture well to our east by Thursday, but
enough could remain on Wednesday to kick off afternoon cumulus
development across the high terrain across LA/VTA counties with a
few showers. No mentionable PoP as of yet.

.LONG TERM (THU-SUN)...26/151 PM.

Ensemble (GEFS, EPS, GEPS) and deterministic models are in good
agreement on synoptic scale features on Thursday through next weekend
as broad trough and west to southwest flow aloft develops. Mean
ensemble 500 mb drop to heights are near normal by next weekend,
and this combined with increased onshore flow should bring high
temperatures back down close to normal.

Gusty northwest to west winds may approach advisory levels for
typical areas late in the week. NBM suggesting gusts of 30+ kts
by Friday afternoon along much of the SBA south coast. The
increase in winds will maintain at least elevated fire weather
conditions for many inland areas, despite the break in the heat
and potential improvement in humidity values.

&&

.AVIATION...27/0036Z.

At 0030Z, the marine inversion at KLAX was based at 700 feet. The
top of the inversion was 2200 feet with a temperature of 29
degrees Celsius.

Overall, moderate to high confidence in 00Z TAF package. High
confidence in CAVU conditions for all valley/desert sites through
the period. For coastal sites, moderate confidence due to
uncertainties in timing of IFR/LIFR cigs tonight. There is
a 40% chance of VLIFR cigs at KSMX late tonight and 20% chance
for remaining coastal TAF sites.

KLAX...Moderate confidence in 00Z TAF. For tonight, high
confidence in return of CIG/VSBY restrictions, but moderate
confidence in timing (could be +/- 2 hours of current 06Z
forecast) and flight category (equal chance of IFR or LIFR).
There is a 20% chance of brief VLIFR conditions late tonight.

KBUR...High confidence in 00Z TAF as CAVU conditions are
anticipated through the period.

&&

.MARINE...26/739 PM.

A SCA remains in effect for the outer waters through late tonight
as there should be some widespread gusts to 25 kt, and up to 30
knots near Point Conception. Gusts to 25 knots will also extend
into the western Santa Barbara Channel, with very short periods
(5-6 seconds) everywhere. There is a high probability of SCA wind
gusts up to 30 knots Monday through Friday over the outer waters,
and also at times nearshore along the Central Coast and in the
Santa Barbara Channel.

Areas of dense fog with visibility of one nautical mile or less
will occur across much of the coastal waters tonight through
Monday morning.

A 12-14 second period S-SE swell of 2-4 feet is expected to build
into the waters from Tropical Storm Celia, likely peaking Tuesday
evening through Wednesday afternoon.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory in effect until 8 PM PDT Monday for zones
      53-54-88-343>345-348-351>353-356>359-363-547-548. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 650-670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/jld
AVIATION...Gomberg
MARINE...Smith
SYNOPSIS...jld/Smith

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox



Area Forecast Discussion

National Weather Service Phoenix AZ

 459 PM MST Sun Jun 26 2022

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Shower and thunderstorm chances will continue across the region much
of the week with the best coverage of storms and greatest impacts
likely today, then possibly again Wednesday. Storms will have the
potential to produce frequent lightning, brief heavy downpours,
gusty winds, and localized blowing dust. Temperatures will remain
near normal with lower elevation afternoon highs exceeding 100
degrees. Cloud cover will keep overnight low temperatures more mild
than usual.

&&

.DISCUSSION...
Quite a convoluted flow pattern early this afternoon featuring a
retrograding southern plains anti-cyclone, building East Pacific
high pressure, and in between an elongated, sheared trough covering
much of Arizona. With one sheared shortwave lifting into northern
AZ, energy from the outer reaches of TS Celia in central Sonora can
be seen separating from the influence of the tropical system and
becoming absorbed in the southerly flow entering AZ. Within all this
synoptic scale detail, visible satellite reveals a well defined,
compact MCV ejecting through SE AZ with notable moist ascent. KPSR
12Z sounding data sampled a rather unimpressive moisture
distribution with mixing ratios in the lower troposphere only 6
g/kg, however objective analysis indicates a pool of 9-10 g/kg
values lingering closer to the international border. In fact, recent
ACARS soundings showed 8-9 g/kg already streaming back into the sfc-
H8 layer around the Phoenix metro.

Given all these features, it`s not incredibly surprising that CAMs
continue to highlight a convectively active day through much of the
Arizona portion of the CWA including most lower elevation
communities. The aforementioned MCV was inhibiting instability
growth through SE AZ while marginal moisture profiles were limiting
MLCape elsewhere through the region early this afternoon. However,
the overall favorable upper divergence and ascent structure has
allowed the first storms to quickly develop over mountain areas with
minimal instability; and ample heating and improving moisture over
Maricopa County and vicinity should provide an environment for
convective sustenance once storms descend into lower elevations.
Inhibition appears lower than the past several days such that only
one dominant outflow may be sufficient to initiate new updrafts and
spark new storms, but certainly colliding outflows would be optimal.
At this time with uncertainty over deep convective development in SE
AZ given the cloud cover, a northern generated outflow may be the
overwhelmingly predominant feature this afternoon and evening.

With MLCape likely reaching a 500-1000 J/kg range and DCape
exceeding 1500 J/kg, HREF probability of 30+kt gusts continues over
70% across much of Maricopa County between 4pm-9pm. A few severe
(50+kt) gusts would not be unexpected, but highly dependent on
outflow/storm relationship and individual cell interaction.
Regardless, SPC has placed the eastern CWA within Marginal severe
risk this afternoon. Similar to the past several days, strong winds
and blowing dust will be one the greater potential impacts, with
only cell motion and lower moisture values limiting a greater flash
flood threat (a few isolated location may still experience
flooding). Based on all available information, the Gila Bend to
Buckeye corridor (and surrounding communities) looks juxtaposed for
the combination best suited for the strongest, most impactful
storms.

Scattered afternoon and evening storms will be possible again
Monday, however both CAMs and global models suggest far less
thunderstorm coverage. Assuming the convectively active outlook for
today comes to fruition, one would expect much less favorable
condition tomorrow as the environment becomes partially convectively
overturned with weaker lapse rates and subsidence. Storms would
still be favored over high terrain initiation points, and outflows
still generated, but likely with insufficient support in lower
elevations. Similar story Tuesday as the entire flow pattern
realigns and high pressure ridging temporarily strengthens over
central Arizona. While much will depend on mesoscale details,
Tuesday may be a day with moisture recycling and better ascent
outside the forecast area.

Ensemble members depict central H5 heights peaking around 594dm over
northern Arizona Wednesday before the anti-cyclone edges east again
towards the southern plains. While respectable subtropical moisture
will remain in place (especially by late June measures), increased
westerly cyclonic flow advancing towards the southern CA coast may
begin to battle and erode the western periphery of the moisture axis
across western and central Arizona during the latter half of the
week. Model trends suggest convective activity maximized again
Wednesday afternoon as shortwave energy entering the region feeds
along the moisture anomaly providing POPs in the 30-40% range over
lower elevations. Thereafter the remainder of the week, mandated NBM
POPs fall closer to 15% or below from Phoenix westward while
maintaining a 40-50% range over eastern higher terrain. Ensemble
outcomes diverge more notably over the weekend and early next week
members struggle with the West Coast trough position and magnitude
of moisture erosion over the forecast area. Based on ensemble
distribution, there`s an approximately equal chance that status quo
convective activity continues into next week versus activity
becoming relegated strictly to mountain locations or almost shut
down entirely.

&&

.AVIATION...Updated at 2355Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main aviation concern will be the impacts of scattered to
frequent thunderstorms over the terminals as late as 05-06Z this
evening. Some of the highlights include strong and gusty outflow
winds with gusts in excess of 35 kts continuing from the NE, but
any direction is possible with additional outflows. Low cloud BKN-
OVC storm CIGS could also fall to 6-8 Kft along with storm vsbys
of 2-4 sm and frequent lightning. Once the storms move through,
moderate winds are expected to mostly favor an E component through
the remainder of tonight, notwithstanding late night outflows
from other directions. Skies will remain partly cloudy with SCT-
BKN mid cloud decks near 10-14 kft.


Southeast California/Southwest Arizona including KIPL and KBLH:
At KIPL, southeasterly winds are expected throughout the period at
around 10 kts. At KBLH, southerly winds will prevail at around 10
with gusts near 20 kts during the afternoon. There is a chance (30%)
of a thunderstorm, developing east of the Lower Colorado River
Valley, which could briefly increase the southeasterly wind
component.

&&

.FIRE WEATHER...
Moisture will remain entrenched across most districts through much
of the week with the greatest afternoon thunderstorm and wetting
rain chances focused over higher terrain locations north and east of
Phoenix. However, even lower desert communities may occasionally
experience wetting rainfall at times - more likely during the first
half of the week as storm coverage may decay into the weekend.
Minimum afternoon humidity levels will fall into a 15-30% range with
somewhat lower values in far western districts and a tendency for
lower values towards the end of the week. Overnight recovery will be
poor to fair in lower elevations (20-40%) and good over eastern
district high terrain locations (40-70%). Aside from occasional late
afternoon/early evening thunderstorm downburst and/or outflow winds,
winds should not be a significant impact.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...18/Heil
AVIATION...Sawtelle/Hodges
FIRE WEATHER...18